Gas detection and measurement systems typically collect a sample of gas or a continuous stream of gas from a desired sample site through a tube, and the sample is in turn provided to a measurement apparatus for analysis. In many applications such as respiratory gas monitoring, water and other contaminants may be present in the gases collected and monitored. Various types of filters and water traps are often employed at one or more points along the sample tube to prevent such contaminants from being drawn inside the measurement apparatus, to thus prevent the contaminants from interfering with measurement of the sample and/or occluding the path of gas to the measurement apparatus. Such filters and water traps are often located externally of the measurement apparatus on an instrument panel near where the sample tube is connected to the apparatus, so that the user may readily access the filters for replacement when excessively contaminated. In other cases, such filters may be located internally of the measurement apparatus, thus requiring the instrument to be serviced if the filter needs to be replaced.
Filters and water traps placed near an instrument panel are often an acceptable solution to allowing easy filter replacement. However, an external filter and water trap requires extra space beyond what is needed for the sample line connector. Often the additional space required is not available. For example, many multi-parameter medical monitoring instruments have several plug-in modules in close proximity to one another, or a compact cluster of sensor connectors. In such cases, the additional space needed to locate an external filter poses a significant problem. On the other hand, locating the filter internally of the measurement apparatus creates the problem that the instrument user cannot change the filter when needed, with the result that the measurement apparatus must be taken out of service for maintenance to replace the filter.
Thus, there is a need in the art for a gas sampling system including a replaceable filter that can be removed by a user and that has a sample line accessory connector integrated with the replaceable filter, so that no additional external space other than that needed for the sample line accessory connector is needed.